The invention relates to a fuel pump with a pump stage driven by an electric motor, with a jacket surrounding the electric motor and the pump stage and having an impeller arranged rotatably between two casing parts of the pump stage, with an inlet duct arranged in one of the casing parts and an outlet duct arranged in the opposite casing part, with rings, arranged in the impeller, of guide blades delimiting blade chambers, and with part-annular ducts arranged in the casing parts and located opposite the rings of the guide blades, the part-annular duct of the inlet-side casing part being connected to the inlet duct and the part-annular duct of the outlet-side casing part being connected to the outlet duct.
Such fuel pumps are often used for the conveyance of fuel out of a fuel tank to an internal combustion engine in present-day motor vehicles and are known from practice. The casing parts of the known pump stages are manufactured mostly from metal or sintered ceramic, in order to achieve an intended stability. For example, as a result of holding forces of the jacket or owing to temperature fluctuations, forces are introduced into the pump stage, which lead to a flexion of the casing parts. Furthermore, a return body is supported over the entire circumference on one of the casing parts of the pump stage and is braced radially with respect to the casing part. Both axial and radial forces are therefore introduced into the casing part, thus likewise leading to a flexion of the casing part. However, a flexion of the casing parts leads to a variation in an axial gap between the casing parts and the impeller. Moreover, a pressure generated by the pump stage in the electric motor leads to a reduction in the axial gap between the casing part arranged nearest to the electric motor and the impeller.
The known fuel pump has the disadvantage that it is highly cost-intensive to produce because the casing parts of the pump stage are manufactured from metal or sintered ceramic.
The problem on which the invention is based is to design a fuel pump of the type initially mentioned, in such a way that it can be produced particularly cost-effectively and a flexion of the casing parts of the pump stage is largely avoided.